For a structure:
long int zip;
To declare a structure pointer:
struct address *address_pointer;
Uses of structure pointers:
1) For the creation of linked lists and other dynamic data structures that depends on dynamic allocation.
2) To pass a structure to a given function using call by reference method.
Advantages of using structure pointers:
1) Fast function calls are possible.
2) Only address is passed and not the entire structure.
3) Even the contents of the structure can be modified by the function call.